Welcome to the Community!
I'm sorry to hear about the connection speed trouble you're experiencing.
I pulled up your account using your community details, to check what's going on. I ran some tests and we're not detecting any network issue. At the moment, your modem is registering a download speed of 15.2Mbps. It seems like the trouble could be the transfer of data from the modem to your devices. There's a possibility that the issue could be WIFI-related as well.
I understand that you mentioned that you spoke to our Helpdesk Team yesterday. I checked our records and found out that the call was disrupted due to an emergency situation brought by an earthquake.
I'll organize a call from a Sr Technician tomorrow to follow up and continue with the troubleshooting. Please expect the call between 10AM-11AM QLD.
Our records show that you have been contacted by our Technical Team but they were not able to reach you yesterday. However, it seems like you did ring back and was able to speak with a Helpdesk specialist.
Based on the notes, the issue with the speed was pointing to your Chromecast and WIFI interference. A WIFI channel change helped in resolving the issue.
If you have other concerns, feel free to leave a message.